I'm not sure what exact law of classical physics you're referring to but it doesn't sound correct.

On a similar subject, centripetal/centrifugal 'forces' are not physically real forces like electromagnetism or gravity. The former is actually a condition for circular motion, and the latter is the result when you analyse a problem in a rotating coordinate system.

Ah, yes, it is true that an accelerating charge will emit electromagnetic radiation and lose energy in the process (a result from electrodynamics). It's a result you can derive from Maxwell's equations.

I'm not sure how this applies to a planet which is, after all, rotating and made up of charged particles (though the planet as a whole is more or less electrically neutral). Perhaps the effect cancels, or the accelerations are far too minute to produce a measurable effect?

Staff: Mentor

The earth is extremely close to neutral, all charges are accelerated in a similar way, so we do not emit (significant) electromagnetic radiation based on our orbit around the sun.

Earth has a gravitational charge (=a mass), and emits gravitational waves. However, Earth is slow relative to the speed of light and gravity is weak, so the lost power is tiny: just ~200W. If there would be no other effects on the orbit, the radius of earth would decrease by about 1 femtometer per day. About 2 millimeters in the whole lifetime of the solar system.